Protection Against the Oxidation of Composite Material Parts Containing Carbon and Parts thus Protected

Abstract

A part made of a composite material containing carbon, having an open internal residual porosity is protected against oxidation by performing at least one stage in which an impregnating composition is applied, said impregnating composition containing at least one metal phosphate and titanium diboride. Efficient protection against oxidation is thus obtained at temperatures of more than 1000° C., also in the presence of a carbon oxidation catalyst and in a damp medium.

Description

BACKGROUND OF THE INVENTION [0001] The invention relates to providing parts made of composite material containing carbon with protection against oxidation, and in particular parts made of thermostructural composite material comprising carbon fiber reinforcement densified by a matrix that is constituted at least in part by carbon. [0002] Thermostructural composite materials are characterized by their good mechanical properties and by their ability to conserve those properties at high temperatures. Nevertheless, in an oxidizing medium, this ability to conserve good mechanical properties at high temperature depends on the presence of effective protection against oxidation. Whatever the way in which such materials are prepared, they inevitably present residual internal pores that are open and that give oxygen in the surrounding medium access to the core of the material. [0003] In addition, in certain applications, in particular brake disks of carbon / carbon (C / C) composite material as us...

AI Technical Summary

Benefits of technology

[0007] An object of the invention is to provide a method enabling parts made of composite material containing carbon to be protected against oxidation, the method being easy to implement and being effective even in the presence of oxidation catalysts, in the presence of moisture, and when exposed to high temperatures, greater than 1000° C.

[0009] In known manner, titanium diboride TiB2 behaves as a reservoir for very progressive formation of oxides such as TiO2, B2O3 which are capable of conferring to the protection against oxidation a barrier characteristic against diffusion of oxygen from the surrounding medium, thereby enabling high temperatures to be withstood, i.e. temperatures above 1000° C., and typically up to 1400° C. or higher.

[0010] Above all, by associating with the element phosphorus P present in the composition and with a metal Me coming either from the phosphate precursor used or from exposure to a catalyst for oxidizing carbon and coming from the outside, TiB2 is capable of forming complex oxides of the Ti—O—P-Me type. Forming such oxides thus enables the oxidation catalyst coming from the outside to be trapped in the form of a glass, i.e. above 1000° C. The glass formed in this way also contributes to the oxygen diffusion barrier effect up to at least 1400° C. while being insoluble in water, i.e. while enabling stable protection to be obtained in a moist medium.

[0020] A preliminary step may be performed of treating the composite material part by impregnating it with an aqueous solution of a wetting agent, and then drying the aqueous solution so as to confer on the composite material wettability that is increased by the presence of the wetting agent.

[0021] According to another implementation feature of the method, it may include a step of applying a solution of at least one metal phosphate without any solid filler, prior to applying the composition containing at least a metal phosphate in solution together with titanium diboride, and possibly other solid fillers. Because of its smaller viscosity, the solution that does not have any solid filler, and in particular does not have any titanium diboride, can penetrate more deeply into the residual open internal pores of the composite material. As a result, the protection against oxidation comprises one or more metal phosphates anchored in depth in the pores of the composite material and an association of metal phosphate(s), titanium diboride, and possibly other solid fillers closer to the surface of the composite material.

Problems solved by technology

Whatever the way in which such materials are prepared, they inevitably present residual internal pores that are open and that give oxygen in the surrounding medium access to the core of the material.

The effectiveness of such composition is nevertheless limited above a certain temperature threshold, at around 1000° C., at which temperature the active components of the composition decompose.

Nevertheless, the process of forming complete protection against oxidation then becomes much more complex, since the protection is constituted by two superposed layers, each requiring its own specific implementation process.

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